Objectives: Our aim was to determine the temporal pattern of expression of transcripts encoding the myometrial gap junction protein connexin-43 in the human myometrium during late pregnancy and with the onset of labor. We also correlated these data with levels of total connexin-43 protein and the appearance of gap junctions within the myometrial cell membrane.
Study design: Myometrial tissue was collected during cesarean section from 27 women between 37 and 41 weeks of gestation not in labor and from 7 women between 39 and 41 weeks during active labor. The levels of connexin-43 messenger ribonucleic acid and protein were estimated by Northern and Western analysis, respectively. The appearance of gap junctions between myometrial cells was assessed by immunofluorescence of histologic sections of myometrium from these women.
Results: Levels of connexin-43 messenger ribonucleic acid in myometrial tissue collected from women not in labor increased (p < 0.01) between 37 and 40 weeks' gestation with a further significant increase occurring during labor (p < 0.05). The level of connexin-43 protein decreased (p < 0.05) during late pregnancy and was not increased during labor although gap junctions (which were not present during pregnancy) did appear in the myometrial cell membrane during labor.
Conclusions: These data suggest that the mechanisms responsible for the increased myometrial cell-cell communication necessary for the development of effective labor contractions likely involves regulation at the level of both messenger ribonucleic acid and gap junction formation in the cell membrane.